1. Field of the Invention
The present invention relates to a method of determining structural data of prototypes for a lightweight technical structure, to the practicing of the method of producing prototypes and to a prototype produced by the method.
2. The Prior Art
The use of models from nature for technical applications has been known for a long time and comes naturally human inclinations. During the course of evolution, nature has by natural selection created extremely energy-efficient structures and processes in response to the quest for the best strategy in the permanent struggle of the species for survival. These structures, even though for different reasons, seem also suitable and desirable for many technical applications. However, the conversion often fails because of the difficulty in directly applying the biological system to the desired technical system. The basis of such a conversion has to be, on the one hand, an exact study of the morphological structure of biological systems including the natural materials and their characteristics and, on the other hand, an intimate knowledge about their purpose, i.e. the overall connection of the observed system in its natural environment. Only such a comprehensive understanding from a biological-technical point of view enables a designer to structure technical systems on the basis of biologically effective mechanisms. The science of the systematic technical conversion of biological structures and processes into the technical field is generally referred to as bionics or biomimetics.
Many publications deal with interpreting such principles and with the presentation of the current state of the art. Publication I (Werner Nachtigall, “Vorbild Natur—Bionik-Design fuer funktionelles Gestalten”, Springer Verlag, 1997) describes the basic principles of natural structures [I, p. 21 seq.]: Nature does not construct additive components maximized to individual main characteristics, but it develops integrated systems optimized in respect of the sum of its requisite characteristics. In nature, the system of energy to be acquired by food intake is confronted by the energetic effort of defense/fleeing on the one hand and of reproduction on the other hand. The more effectively energy can be applied, the greater is the chance of survival. Light yet sturdy structures and detailed adaptions to the most variegated environmental conditions are the result and represent a vast pool of designs which can be utilized by technology. The lotus effect may serve as the best known example of bionic design [I, pages 43-44]. In connection therewith it was possible to demonstrate that surfaces, e.g. those of leaves, very effectively prevent the attachment dirt particles and water droplets by a defined distribution of micro-roughnesses by water droplets not adhering to the surface but, because of their surface tension, roll across the tips of the roughnesses, absorbing on their path, and taking with them, the dirt which is also attached only to the tips of the roughnesses. This ability enables plants effectively to clean themselves and in doing so to maintain the light absorption necessary for their survival at a high level. This self-cleaning effect can also be on technical surfaces by coating with other materials simulating the roughness of plant leaves. This makes it possible significantly to reduce the otherwise necessary cleaning not only of, for instance, solar cells for maintaining their light absorption, but also of optical surfaces such as facades of buildings and window panes. There are a number of further examples from the animal kingdom such as, for instance, the utilization of the flow and anti-fouling action of whale skin, the direction-dependent generation of friction of snake skin, etc. However, the publication [I, pages 127-130] offers no detailed description of the model formation in the step principle—zero-model—final version (FIG. 67) required for any technical conversion of such analogies.
Publication II (Claus Mattheck, “Design in der Natur—Der Baum als Lehrmeister”, Rombach Ökologie, 1997) [II, Pages 13-18, 45-47] relates to the mechanism of biological self-optimization, i.e. the optimization of the use of energy, based upon the example of the adaptive growth of trees. Because of the constant changes of its living conditions during its life-time, the trunk of the tree is subject to various stress conditions as a result of wind, sun, soil composition, etc. By its genetic disposition the tree is enabled to counteract unfavorable distributions of stress by the growth of different thicknesses between positions which are endangered and positions which are not endangered. It always aims at a chronological average at constant stress acting on the entire surface of the trunk of the tree. The same conditions govern other mechanically highly stressed components in nature, such as bones, teeth, claws or talons and the like. The underlying principle, the axiom of constant stress, may be considered to be the basis for biologic-technical construction. Here, too, it is evident that the energy-optimized design of nature, i.e. a component of a weight minimized by elimination of stress-free zones for exerting the force necessary for an intended application, satisfies the model function for ecologically and economically optimized technical structures. The description of the approach for converting ecological designs [II, pages 63, 64], being the closest prior art from which the invention is proceeding, briefly describes the applicable methods and their interaction. The technical object initially provides the relevant basic parameters for the technical design of a structure to be produced. This may, for instance, be the approximate dimensions of a component (limiting measures), effective external loads and the peripheral conditions (fitting, support, guiding). For instance, by the finite-element-method (FEM), mechanics will provide, as numerical tools, stresses, expansions and deformations occurring in the structures. Non-supportive structural areas can then be eliminated by the so-0called soft-kill option (SKO). Thus, a model of a light structure may be made available which may yet suffer from problem zones. These may be subjected to post-treatment with the so-called computer aided optimization (CAO) by further shrinkage and alteration of the structure so that in the end the structure to be designed will result as a lasting light-weight structure by a iterative optimization process. The extent of the optimization process depends directly upon the quality of the prototype. The closer this resembles the complete final structure, the fewer will be the steps leading to optimization. However, overall only relatively simple structures can be converted, and according to the state of the art even the designing of the data-based prototype following a model from nature requires extensive conversion and calculating processes. The only aid in this respect has hitherto been the use of a very simple prototype which, however, only transposes the complex calculations to the final structure since the deviations from the prototype are very large.
Publication III (Hamm, Merkel, Springer, Jurkojs, Maier, Prechtel, Smetacek, “Architecture and material Properties of diatom shells provide effective mechanical protection”, Nature, Vol. 421, pages 841-843, February 2003) deals with the specific and variegated structural formation of diatoms as a protection device. The shell structures of unicellular organisms and, especially of bacillariophycea (diatoms, phyto plankton) and phaeodaria (radiolaria, zooplankton) play a decisive modeling role with respect to mechanically stressed light components for structures in mechanical engineering or mechanical esthetic creations in architecture. This field offers a great variety of structures the main purpose of which is to provide protection against mechanical loads and destruction in a functional context with their food competitors and predators while at the same time minimizing their weight, i.e. optimizing the use of energy. About 60,000 types of diatoms of two groups or orders are known which because of their shell geometry are divided into centric (centrales) and pennate (pennales, bow-shaped) ones. The skeleton-like support frames of the diatoms are formed of silicic acid, i.e. the oxy acids of silicon SiO2.nH2O. Depending upon their water content they are known as ortho-, orthodi- or meta-silicic acid. Without water silicon dioxide or silicic anhydride SiO2 would remain. With a minimum of material diatoms create a maximum of strength and thus have the same purpose as modern light structures.
Publication IV (“Wunderschöne Kieselalgen: Muster für stabile Konstruktionen”, Alfred-Wegener-Institut für Polar-und Meeresforschung, Http://www.awi-bremerhaven.de/AWI/Presse/PM/030219 diatomeen-d.html setting forth several technical data relating to diatoms and (Internet) Publication V (“Jugendstil im Meer”, Forschungszentrum Jülich, http://fz-juelich.de/portal/index.php?jahr=2203&index=281&cmd=show& mid=125) with photographs relating to the standard test method with glass needles for the mechanical stability of bio-mineralized unicellular organisms.
In conventional designing a drawing is prepared which approximates as closely as possible the technical requirements of the structure to be fabricated. The designed structure is then fabricated, by appropriate fabrication techniques, as a prototype, and tested. If it satisfies the set requirements, i.e. if it withstands loads of a desired range and its service life is adequate without changes impairing its function, it is converted and placed into series or mass production. Otherwise, its critical spots will be reinforced. No weakening is carried out of excessively dimensioned spots since they usually are not known. A progressive construction process will optimize the structure by creating a FEM model, testing it by a computer under required stress conditions and, where indicated, improving it. Even here, however, stresses or tensions are simply reduced by reinforcements. The process does not serve optimization in a general, that is to say ecologico-energetic since; its aim is rather to avoid trial-and-error-steps and thus constitutes optimization only in terms of the time of development. Moreover, in accordance with classical teaching of construction, complete systems are hardly ever optimized from several components. Nevertheless, publications I, II and III leave no doubt that the development of energetically optimized structures and, more particularly, lightweight structures must be to everyone's benefit. Conventional methods attain this goal only by high complexity in terms of calculating time and capacity. It will thus be apparent that the production of a prototype constitutes a decisive step as to an ecological development of structures capable of withstanding high loads. The more closely such a prototype approaches the required conditions the simpler will be to adapt and optimize it for an energetically optimized structure which can be economically produced. At present, a designer can accomplish this at best in any given very narrowly defined special field and only for individual components or very simple systems. However, highly precise prototypes of complicated structures relating to different technical fields cannot be fabricated.
German laid-open patent specification DE 100 53 299 A1 (“Method of designing a component and wiper unit component”) discloses, by way of example, an approach for designing mechanical components by computer-aided methods. The method steps include a forming a physical model (model room model), describing the model with its finite elements and using a 3-D program for generating a data model. Furthermore, method steps are disclosed relating to optimizing topology and shape. The example of the application discloses the complexity of obtaining data for a prototype. The methodology of creating a physical model followed by a drawing—nowadays it is oftentimes a data model—or vice versa first a drawing and then, possibly computer-assisted, a physical model, is used in a plurality of variations without providing suggestions for an improved collection of prototype data.
The mentioned publications offer no rational method of creating a suitable prototype by means of which the necessary optimizing work as to a particularly advantageous lightweight structure can be minimized. There is no disclosure of any direct step from the technico-biological study of natural architectures and processes within the ambit of bionically released analogous tests and is thus relegated to a purpose-directed interdisciplinary team of biologists and engineers. In this context, the method to be selected depends upon the subject of the investigation and the technological possibilities of the participants. No presentation is being made of a generalizing methodology which can be adapted to different required profiles.